TechStuff Gets a Bright Idea

you know, we start the episode off pretty traditionally. One of the things that we had as an early ritual as we recorded Tech Stuff was Jonathan and I would be sitting here in the virtual darkness and someone we had different engineers over the time, over the years now, but someone would come in and turn on the lights and good lighted begs. But we wanted to talk a little bit about light, specifically light bulbs to day. So

what a brilliant idea of those were? You know, before lightbulbs, Before light bulbs, there was no way to indicate that you had an idea. Yeah, yeah, there's no there's no yeah, pre light bulb there was no ting before we get into how light bulbs work in their history and everything. I want to lay down a little physics for you. All right, go ahead and enlighten us. I see, So we are talking about light and what is light. Well, light is made up of these very tiny particle like

packets called photons. They've got energy, they have momentum, but there's one thing they do not have charge accounts mass or I was going they have no mass, but not no moss. Photons are these packets of energy. They have momentum but not mass. And these particles, these these photons are emitted by atoms. Once you have excited an atom to the point where it's electron starts to move out of its normal orbit and goes into a further orbit

from the atoms nucleus. And once once you remove the energy source from that atom, the electron will eventually return to its normal orbit around the nucleus. But it has to it has to get rid of that energy that you have pushed into it. Right, Energy is not created or destroyed, it's just transferred. So this electron, as it's coming back down to its normal orbital is going to shed off energy, and in this case the energy is in the form of photons. Now, photons are going to

be emitted in the entire spectrum of light. Now humans we are capable of perceiving a narrow band of that spectrum called the visible spectrum because it's visible to us. Oh, I always wondered about that. This is where the whole ROYGBIV thing comes in, right. The different wavelengths of light dictate what the color is as we perceive it. Uh. The but the the light goes well beyond outside the

the visible range. There's things like ultra violet and infrared, and then you get into electromagnetic radiation as you go further out. But and anyway, Uh, these photons can come into various forms, so you can have a infrared photon or ultra violet photons. So uh, if it's in the visible light spectrum, we're able to see it. Now that's important because that's the whole basis of creating a light bulb. As you want to create some sort of device that you can used to create photons so that you can

illuminate an area. And before light bulbs, you didn't really have that option unless you set something on fire. Uh. And there's a limited number of things we can set on fire before we set ourselves on fire, or we run out of stuff that is flammable, So it was a good idea to try and develop something that could create light in another way. Now, uh, how do we know about how what is the principle upon which light

bulbs work. Well, again, if you excite an atom and you push those electrons out, when the electrons come back in, they emit photons. If you give enough energy to an object, then you can emit enough uh photons for it to be within the depending upon the nature of that material, for it to be within the visible spectrum for it to be perceptible. Because even if it's in the visible spectrum, if the energy is not great enough, you won't be

able to see it. And we're all emitting energy all the time, like humans are emitting infrared energy all the time, and if you had an infrared camera, you'd be able to see it even in perfectly dark room. You look at the infrared camera, look at a person, you would see light as interpreted by the sensor in that camera and converted to visible light for us to see. You would be able to see that person because they're emitting

that infrared light. Well, we may even depending on what what, depending on the material, it may even be emitting visible light. But it might be emitting at levels so low as to be imperceptible to humans. So if you add more energy, you can boost that and actually see the visible light. Uh.

And this can happen with things like solid materials. And there was a fellow named John William Draper who in eighty seven demonstrated that solid materials, almost all of them, will glow once they reach a temperature of seven kelvin. Kelvin's a scientific scale for temperatures. Kelvin is what we have when you get to zero kelvin. That says that as cold as you can get, it actually refers to molecular movement, and at zero kelvin, there is no molecular movement.

So that's like the deepest depths of space where there's nothing absolutely absolutely uh So, if you wanted to convert that into degrees that we're more familiar with most of us anyway, it would be about five and twenty five degrees celsius or nine seventy seven degrees fahrenheit, And at that temperature solid materials will start to glow. We call

it the Draper point. Now, in order to have a object glow at a uh at a at an intensity bright enough for it to illuminate, say a room, you will have to put in more energy than that, right, because this is talking about they start to glow, but that doesn't mean that they're glowing so brightly as to illuminate an entire room. That's where it starts. So but

you know, you've you've probably seen this. If you've ever seen a blacksmith work, then you know the blacksmith might be heating up iron and when they take that out it's glowing red. Or a glass blower or lava. You know, there's lots of stuff that tends to lava. It's not all manmade, but there's lots of stuff out there that um that that demonstrates this. So that's the principle. But but the idea behind an electric light source actually predates

Draper's discovery. Really yes, back in well the early eighteen hundreds. I've seen I've seen reports from eighteen o six all the way up to eighteen o nine. There's some discrepancies there. But an English chemist and inventor named Sir Humphrey Davy, named Humphrey Davy, he was designated a night So that's the sir. He connected a battery to a strip of charcoal, and he used the electricity to actually heat up the charcoal to the point where it started to glow, which

created technically the first electric arc lamp. Uh. This was not a viable means of illumination as it was hard to do. It required a lot of energy. The battery drained really quickly, the carbon burned at such a or it got so hot as to be incredibly dangerous for uh, say, I don't know a typical house um. So it was not something that was going to immediately be adopted into

every household, but it was proving a concept. Uh. Also, by the way, Sir Humphrey Davy did go on to invent many things, including the Davy lamp, which was not an electrical lamp. It was a gas lamp. There was a gas lamp that had a mesh screen that would surround the flame so that miners meaning people who mind the earth, not people who are underage miners, could take the lamps, although depending in England at that point in time, the two may have been the same. Aim. Hey, our

history has not always been a nice one. But the miners could take a lamp down below the ground, and even if they encountered a pocket of gas. The mesh would actually, this fine mesh would prevent the gas and the flame from making friends and becoming a big boom. Very important for miners of both types. So the he did invent that, Again not electrical, but I thought it was an interesting aside. Moving ahead back in the eighty one, Frederick de Moulins, and I'm sure I have completely mispronounced

his name, and I apologized profusely for that. Another Englishman, Yeah it could be. He patented a light bulb in eight forty one, and this one was comprised of a glass case and a burner or burners actually made of carbon and in expensive material you may know as platinum. Yeah, you thought that led light bulbs were expensive, so uh he he patented that design. Again not really practical for for every day or even industrial use. An American inventor named J. W. Starr received a patent for a light

bulb that used a carbon burner. Um and then the next few decades were spent among inventors trying to find a way to perfect the discoveries these earlier inventors had found, so that you could create a light bulb that made sense, that that was efficient, that could light well, that was not going to be prohibitively expensive. And there are two names in particular that pop up all the time, one of them being probably the most famous uh connected to

the light bulb, which is Thomas Edison. Yes, it's funny, as we were recording this, we are rapidly approaching the hundred thirty third anniversary of the first test of Edison's incandescent light bulb. Yeah. Now, it is important to note Edison was not the person who invented the light bulb. He was not even the person to invent the incandescent light bulb, but he was someone who perfected that design

and made it viable as an actual product. Yeah. Now, it's it's important to note, um that these these early lightbulbs, uh, you know, not only were homes not really wired. Actually, the light bulb, I would argue, based on my research the over the past, you know, the past times that we've done tech stuff, we've talked about Edison and Tesla and the lightbulb actually was sort of the key to

getting homes wired for electricity. Yeah, I mean you and it made sense because suddenly you had households that could be uh safely with air quotes around that lit after dark and extend the useful uh time human being could get stuff done, because otherwise, when night fell, we might as well just go to bed because it was gonna be pretty dark. Well, you know, we're early to bed and early to rise, as they say, early to bed, early to rise, because otherwise you're barking your ship on

the coffee table. Well, yeah, that's that's true. Well, gas lamps, uh were very very popular. But they were I mean, in addition to being obviously inherently somewhat dangerous um and oil lamps, but they were um smoky, um. They were dirty, so you know, I'm sure they probably didn't smell all that great um. But the problem with these early light bulbs is that they weren't very practical. O. Hey, look I got yeah, well, so much for that one. Another one.

There was another inventor, an Englishman. The Englishman named Sir Joseph Swan, who was working on light bulbs around the same time as Edison. And Swan's bulb used carbonized paper as the burner, which worked pretty well except that it didn't last terribly long. And in fact, this was a problem that a lot of lightbulb. Researchers were encountering that,

including Edison. The first problem was, all right, well, we've we found uh that if you if you run enough electricity through some sort of object, you can heat it up enough so that it begins to glow. But if that item is exposed to oxygen, then it will burn.

So even if you found a material that does not melt at a high temperature, it would burn, it would combust at a high enough temperature because it'd be you know, it would be adjacent to oxygen, which you know that that's part of the fuel you need, you know, in order to have a fire. UM. So the you had to close it off from oxygen, which is why they were these these vacuum tubes essentially is what they create, these vacuum containers. UM. But once they got through that,

they had to find what's the right material to use. Actually, what Edison ended up using at first was bamboo. He took Japanese bamboo and carbonized it and created a filament. In this case, what a filament is is this really long, long, long, long strip of material that is then coiled so that you can decrease the space that it needs to um to fit into whatever you want to put it in, so it's got a lot of surface areas. Then the resistance is high. A resistance in electricity is the the

materials resistance to electrons flowing through it freely. The more resistance there is in general, Okay, you've got greater resistance, you have greater heat. Well, the secret to the light here is the amount of heat that's being generated. That's the energy that is creating this whole system of electrons being pushed out and then when they start coming back in, the photons are being let out. So let let the photons out? Who let the photons out? That was as

an a swan as it turns out. Um, it's interesting because then Edison Edison ended up hiring what his first his first light bulb design used a temperature controlled switch to try and keep the material at the right temperature so that it would the light bulb would remain lit longer. Because that was an early problem with these light bulbs is that their their utility was low because they couldn't

you couldn't burn them for very long. But this was a problem because the the temperature control controlled switch, once a certain temperature was hit, it would switch off right, the light would go off, and so it started creating this flickering problem and made the bulb practically unusable. So he then hired a physicist from Princeton named Francis Upton, who led Edison's research team working on light bulbs, to start practicing with other stuff. That's when they came upon

the idea of using the bamboo as a filament. Um. Swan and Edison ended up battling each other. Edison ended up taking patent lawsuits against Swan, but then ultimately the two of them formed a partnership together and they created the Edison Swan United Company. Teamwork, teamwork. Um. Yeah, just so, just so you guys know, patent wars are not a new thing. Oh no, not in the least. Um. Yeah,

it's funny. While u while carbonized bamboo sounds like an ingredient for a hipster sandwich, Um, it did have the ability to burn for more than which you know, back in that time, that was pretty nice for a for a light bulb. Yeah, and uh, this served as the basis for what future light bulbs would be. And then we ended up shifting to a different type of filament. But we'll get into that in a second. So let's talk about the basic anatomy of an incandescent light bulb.

And don't worry Floresce in an L. E. D. Fans, We're gonna get to you too. You just sit tight. So the incandescent bulb, You've got two contacts to two electrical context on this on a typical incandescent bulb. One of them is at the very end of the bulb, that's the base of the bulb, and the other is in the actual treads that you screw into your um light bulb socket. Yeah. Actually usually has a squeaky noise which has that perfect pitch to give me the heavy gbs.

It's like the fingernails on the chalkboard type thing. It's like almost every single light bulb in my house makes that noise. And so it's a physically demanding task for me because well, I guess psychologically really more than physically, because because I I suffer trauma. One follows the other. How many how many Jonathans does it take to you screw in a light bulb? Yeah, well, after the first one, it takes a few others to common down. Yeah, I'm

not afraid of the dark. I'm just afraid of changing light bulbs, so that's not really true. I just don't like doing it. But anyway, these mental contacts are what create the the circuit, right, so that the circuits complete. When these two contacts are are in contact with the rest of the electrical system. On um, the contacts are attached to some wires and those wires are attached to the filament. Now, in this case, the filament is no

longer bamboo. For your typical incandescent bulb, it's usually tungsten. And the reason why it's tungsten is a couple of different reasons. One is that the melting temperature of tungsten is really high, so you can heat tungsten up quite a bit and not worry about it being um melting

away that. That's obviously another issue with light bulbs. Right you heat up materials, some material is gonna melt, and it might melt before you hit that draper point, which would be bad because you wouldn't get any light out of it. You would just get a you know, a glass cylinder of hot molten sludge. Um Hot molten sludge would be a great name for a band. It is, uh. It is, however, very thin the filament is very thin.

As anyone who has uh smacked a light bulb hard enough to break the filament but not hard enough to break the glass knows that's really annoyed. That's another really annoying thing about changing lightbulbs. Oh when did I yeah, just ruined a perfectly good bye bulbs. So, yeah, it's very thin. Again, that's to increase resistance. That's another thing, is that a a a copper wire, for example, the the greater the diameter of a copper wire, the lower the resistance. So if you have a very um thin

copper wire, the resistance is greater. That means it's going to also generate more heat as a result. Well, this tungusten same thing. I mean, this same principle applies across all materials. U tungsten filament is very very very thin. It's actually coiled twice. The first coil is done to decrease it's you know, the length, and then after you've

coiled it once, you coil it a second time around. Uh. These these support wires, and uh that helps when the tungsten heats up, it starts to generate, you know, give off these photons. Uh, it helps, Uh, concentrate that light so that you have enough for it to be useful, because again, you want to give enough energy there for you to have visible light that you can actually see stuff by, but you don't want to have to pour in more energy than was necessary. And we should point

out incandescent bulbs not terribly efficient. No, we think about heat being a a wasted form of energy in this case, and how hot and incandescent bulb gets. And it's also giving out photons outside the range of visible light, so you're getting you know, infrared light and maybe even ultraviolet light from from these light bulbs. Well that that means that again it's a drop in efficiency. I mean, yeah, it's giving off light, but we can't see it, so it doesn't do us any good, not not in a

normal application. Anyway. You know, if you're doing something that required infrared or ultraviolet light, than sure, although there are better ways of doing that than using a regular incandescent lightbulb. Yeah, I mean you you could. You could even cook brownies with it, which is with an easy bake oven. It's funny because I don't think people, not everyone realizes this.

It's not like a secret. But um, the the older easy bake ovens, especially they're they're essentially using the heat from a lightbulb to cook uh, you know, very simple cakes and brownies and things like that. Right now, the you know, you might ask what's inside a lightbulb? Besides all this stuff, there's actually a gas that's inside most incandescent light bulbs, and it's usually are gone, which is an uh it's an inert gas, meaning it does not react to other stuff. Hey, are gone gas. It's a

tornado outside. So like, oh, you never do anything now that you want it to be inert because obviously, like something like oxygen, then the tungsten would start to burn. It would dramatically decrease the life lifespan of your average light bulb. So they pump the oxygen, They pump air out of the glass globe and fill it with our gone gas. Yep. And so you might say, well, why why not just have a vacuum inst of our gone gas.

The reason for that is that, uh, at that high temperature, you have another problem besides combustion, even if you don't have oxygen, the other problem is evaporation. Atoms from the tungsten will actually evaporate off the filament. Because of those high temperatures, and over time, that means that you're losing you know, every time you're using that light bulb, you're

losing tungsten with the old light bulber. Yeah, and with the old light bulbs, you would actually have the tungsten start to evaporate away and coat the inside of the light bulbs, So the light bulb would get more and more dim both because there was less filament to light and because all the filament that was gone is now coating the inside of the light bulb making it darker. So uh, by using argon, what it actually acts as

is sort of a sort of a barrier. These atoms from tungsten will come off the filament, bump into a an argon atom, and then because argon's a nerd, it's not going to act with that that um uh energy or that that particle. Rather, the particle then returns to the strip of tungsten um. So it acts as kind of a cushion. It's just pushing the the atoms back to the tungsten. Keeping that filament last to last longer very important. And so that's the basic premise behind these

incandescent bulbs. The a uh, you know, they get to a pretty hot temperature. We're talking around degrees celsius or four thousand degrees fahrenheit um, because again you want to put out enough visible light for it to be useful. Now that all depends on the wattage of the bulb. Yeah, which generally speaking, you can think of his brightness. Um, it's it's kind of or or really you can think of his brightness or how hot that tungsten's getting inside

the light bulb. That's what that kind of translates into. Uh and uh. Interesting. We have an article on the site how light Bulbs Work and how stuff Works dot com. Great article, great illustrations, a fun read. I mean, I really do mean that. It's actually you would think it's an article about light bulbs, but it really is a fun read. And one of my favorite uh facts in this is that a typical sixty what bulb has a tungsten filament that six and a half feet or two

meters long and one hundred of an inch thick. I don't have the centimeters for that, sorry, but it's you know, six and a half feet long or two meters and if you were to completely uncoil that filament, however, once it's all double coiled. It's in a space that's shorter than you know, the tip of your pinkie finger, and you're thinking, wow, that's to go from six and a half feet to that is pretty impressive, you know. And again that's packing all that material in so it can

give off enough light for it to be useful. Yeah, now do you uh, do you happen to know how three way light bulbs work? I do not. Actually, as a matter of fact, we have another very very short article on how three way light bulbs work and it they also have to filaments. Um, it's it's very interesting. Now the socket has to accommodate that because it has

to do also with a connect on the outside. But essentially what happens is that the socket is, you know, through a switch, providing instructions on which of the two filaments to light. So for the first on switch, if you've ever used the three way light, you know that the first one is the lowest setting uses the least amount of electricity. Well, the one filament that is designed

for that lower setting comes on when you click the switch. Again, that provides instructions for the second filament, but only the second filament to come on, and then the third the two team up. I see so, and then that the next is off. Got you. You get these the sum total of light coming from the bulb, which is if your pardon upon a brilliant weight. I do that because it's very simple, shiny. So moving on. That's a little just aside and firefly reference for you guys out there.

And of course you can achieve different effects to with the kind of glass. You might be wondering, you know that the what the natural lighting or the what does the blue what's the blue one do? Well, it's just diffusing the uh photons given off by the tungusten inside the light bulb a little bit different. And I should point out an eat that depending upon the material you're using,

that will determine what kind of light is given off. Right, So tungstens giving off this light uh, partially because of the fact that it's tungsten, But other materials give off different kinds of light, different colors of light along or or essentially lights that are different wavelengths, right, so different

parts of the spectrum, sometimes visible, sometimes not. Uh. This is used in chemistry, it's used in astronomy, it's used in lots of different areas of physics, not just in creating light bulbs or you know, heating stuff up until it glows. But that kind of that's kind of the full discussion on incandescent bulbs. But those aren't the only

kind of bulbs we have. We also have fluorescent bulbs. Yes, um, you might say, well, you know, uh, Edison and later the company that he was directly slash indirectly the founder of General Electric, you know, perfected the incandescent light bulb and uh uh you know, you would think that they would be very upset that the fluorescent came out. Well not really because, as we touched on on our famous or infamous GE series how how the famous that's more, that's the famous series on G E G E was

actually in development of the fluorescent light bulb. Yeah, so fluorescent lightbulbs use a different method of generating lights, so you're not you don't have that physical filament inside a fluorescent bulb. Instead, what you have as a sealed glass tube. By the way, we also have how fluorescent lamps work at how stuff works dot com. So again you should read that if you're interested to learn all the physics

involved in this. But in general, you've got a sealed glass tube and not the animal that Chris was alluding to earlier. It's just completely sealed. Uh. The tube has inside it's some mercury and there's also an inert gas like again are gone. Uh. The inside of this glass tube is coated with a powder that's phosphorus. Now, phosphorus means that when light strikes it, it gives off light. So that sounds like it could be totally useless, except

we're talking about light within the entire spectrum. So even if if you have a certain kind of phosphor, it will um If you were to hit that phosphor with light that's outside the visible spectrum, for example, ultraviolet light, and then that phosphor actually emits visible light, that becomes useful because you can either look at stuff that is in the presence of light that's otherwise outside our our field of vision, or you can create something like of

or escent light bulb that uses light outside of our vision to create light that's inside our vision. The way this works is you've got the electrodes at either end of this tube, uh that are wired to some sort of circuit. Now, the circuit once we turn that on starts to introduce uh, free flowing electrons into the gas. Now, this is different from the filament approach because then you have electrons running through a material directly right, just like you would a wire in a circuit. I mean, that's

essentially what it is with this. It's free flowing electrons going through uh. The gas in this case are gone. It takes a little while for these electrons to be introduced into this this tube, which is why when you turn on most fluorescent light bulbs there's this little flickering moment while it's coming on. Yea because the cause again, the the has to introduce the the free flowing electrons

for this to work. So once these electrons with considerable voltage are introduced, uh, the energy starts to change some of the mercury that's in that tube from liquid to gas. Now, again, when we're introducing electricity into or energy into an atom, it's exciting those electrons, pushing them out of their orbitals uh. And then when the electrons start to come back down to their normal orbital they'll give off photons. With the case of mercury, you're talking about light photons that are

in the ultra violet wavelength range. So again you can you you're exciting the mercury and it's giving off ultraviolet light. We can't see ultra violet light unaided anyway, We're incapable of seeing light at that wavelength. But by coding the inside of that tube with phosphors that are able to absorb ultra violet light and then emit light in the visible spectrum, we can use that tra violet light two

give us light we can see indirectly. We have this intermediary step with the phosphors, So the mercury starts to go from liquid to gas, gives off these ultra violet photons. The vultraviolet photons hit the phosphors, the phosphors absorbed the ultraviolet light and emit light in the visible spectrum, and voila or viola if you prefer, we have ourselves a

fluorescent light bulb. By the way, if you have a black light, you essentially have a fluorescent bulb that does not have those phosphors necessarily on the inside because it's just emitting the ultra violet light directly. Uh And then you can have those wicked uh Van posters light up in pretty colors. All in all, You're just another brick in the wall, thank you. So, uh yeah, I mean

that's the that's the essential way that fluorescence work. And this is also why because they contain mercury why they are so dangerous or potentially dangerous, because mercury is toxic. And if you were to, say, I don't know, drop a palette of fluorescent lightbulbs in a warehouse, you could have a potentially dangerous situation on your hands because you could very much have enough mercury there to suffer mercury poisoning. Yeah,

it's some. It's in a way sort of amusing that so many of my friends remember busting fluorescent lightbulbs fondly because they make out. They make a loud noise. I had one. I was in a bookstore once when, uh and I was just perusing some books, so I'm very much focused on what I'm doing when the employee behind me, who was trying to change out a fluorescent bulb, accidentally dropped the one in her hands from a ladder and it landed directly behind me. And I thought I had

just been hit by a shotgun. Okay, turned I wasn't well and and and at that time it wasn't uh popular knowledge. I probably shouldn't say common knowledge, but popular knowledge. People just didn't know, uh that there was mercury in there. Now, I mean, admittedly there's not a boatload of mercury in there, but you know, it could it could be something serious.

And that's why when you're fluorescent light spurned out, it's a good idea to find someone who can take it and recycle that, not only for safety reasons, but also because you know they can recover some of that material. Now, when you're talking about the fluorescent light tubes, uh, that's pretty much it. I mean you've got the uh the tube of gas with the caps on the end, and you plug it into the uh the light fixture to have it work. Well, there's there's other stuff underneath that

that you may not necessarily see. It's it's covered up by the fixture. UM. One of the most important parts I would argue is the ballast, which is a type of transformer uh um that basically ups the electricity to make it work better with the fluorescent light. Because again, you have to introduce those ions, which is not necessarily easy to do, especially since you've gotten inert gas in there.

So if you ever looked at a compact fluorescent light or curly bulb as I like to call them, UM because I like to do that UM and wonder what the heck the big honking bases that you have to screw into a regular light fixture. That's where the ballast is. The ballast is built into the base of that uh that fixture, UM, which is why it may or may not fit into that incandescent and that that fixture that you bought that would allow you to use a UM

a typical incandescent bulb. Now they say in some cases that you should not use those because they do generate heat and that can uh make the ballast overheat, uh cause a short circuit and possibly fire. You know at the ends on what kind of fixture you have, So keep an eye on that. But if you've wondered what that what that situation is, UM, it's built into the ballast. And the ballast is also in that case what controls the three way There are some three way fluorescent compact

fluorescent lights. UM. The ballast is what makes that possible because it can control the amount of electricity going into the tube. Yeah. It's also important to point out that another big difference between using free electrons moving through a gas. Essentially you're talking about ionized gas or plasma. But I know if you're using free electrons moving through a gas, it does behave differently than it would if those electrons

were moving through a wire. Uh. Now with a wire, you know you have the resistance is dependent upon the composition and the size of the wire in a in gas discharge, which is in the terms of this not something that's gross is uh uh, it's the resistance actually decreases due to current. So when you've got a current going, the resistance begins to decrease through this gas. That's more

electrons and ions start to flow through. They bump into more atoms, frees up more electrons, creates more charged particles. So the resistance is uh is constantly decreasing as long as that currents on, and that can be a problem. If that continues for too long, it'll blow out the electrical components of the the the entire system. So that's another reason why these ballasts are important. They are little safety features that control that so that the current doesn't

continue indefinitely. It stops briefly, but not so briefly as to make the lightbulb turn off, or at least if it's turning off, it's turning off at a rate so fast that we can't really detect it. Uh. You may have noticed, you know, lightbulbs that for us and bulbs that flicker like even when they're on, they're just they're just flickering. And that's generally speaking, that's the ballast that

is trying to control this. And you're talking about alternating currents, the currents running essentially one way and then another way, so it's doing it, you know, and the ballast is working for both directions of current and UH, and some of the older bulbs, the system was not controlled very well, like they might have used a magnetic ballast, which has a slightly slower reaction time than current ballasts that are

UH that are usually based on circuitry. So those older ballasts, you know, it meant that if you had a fluorescent bulb turned on, it might give you that flickering look and you might feel like your workplace is the same one that was in the documentary Joe Versus the Volcano. And that's right, you have a brain cloud. Well, then

you have to go to this volcano. Uh, and encounter three different versions of the same triss And I was see, I was working on a joke about how when you were flying in your hot air balloon and you needed to go higher, you would throughout the fluorescent light fixtures because you know the kind of throw the ballast's overboard. Ironically enough, that's somewhat true. I've changed a ballast out of my fluorescent light fixture in my kitchen and they're heavy.

They it's like a brick. Anyway, Well, we should probably move on to the third type of light bulb by wanting to talk about the LED. Actually, if you look at our article believe it or not, there's an article on how stuff works dot com about light emitting diodes. Yeah, we have articles on all of this, which made this

podcast way easy to research. Yes, yes, But the funny thing is if you look at the diagram, the the cross section that are artists have put together of a light emitting diode, it's sort of in a way resembles an incandescent light bulb because it is a diode inside a casing. Yeah. Now, in this case, the the light of right, the light emitting die, it is a type of semiconductor. Actually, in a way, it's the simplest semiconductor.

There is a diode in general, not just a light emitting diode, but a diode in general is a semiconductor, and it conducts electricity, but not as completely as it could. Right. Essentially, it's a semiconductor has a varying ability to conduct electricity, so sometimes it connect like an insulator, sometimes as a conductor.

It all depends on this stuff. Generally speaking, if you control what what you have is, you've got a semiconductor with two different types of material and it tends we tend to call it N type material and P type material. So the N type material has extra negatively charged particles, so it has a negative charge overall. Then the P type material, I think you can see where this is going, has extra positively charged particles. Yes I'm positive, not just sure,

I'm positive. So you can think of the N type material as having an excess of electrons. The P type material has what we call holes. These are places where the electrons could go. Now, electrons definitely want to get over to the positively charged holes. They want to move to those holes because, as we know, when you're talking about charges, opposites tracked John Marcia. Yes, in in subatomic

particle form. So you've got the negative and the positive materials and they're kind of smushed together in a in a diode. So you've you bond together the N type material to the P type material. So you've got the the negatively charged and the positively charged botted together. And there's an electrode attached to each end. So the N type has an electrode attached, the P type has an

electrode attached. Now, if you don't apply any voltage across this diode, the electrons from the N type material fill up the holes in the P type material, and it creates what is called a depletion zone. And in the depletion zone, the semiconductor becomes an insulator. You know, you've you've got those extra electrons, have filled up the holes that were on the positively charge side, and you've reached sort of a neutral ground, right, So depletion zone is

that neutral ground. There are no free electrons or empty spaces, so it's just kind of there. But if you want to get rid of that depletion zone, then you need to push electrons across, moving from the N type area

towards the P type area. And then to do that, you just connect the the IN type side of the diode to the negative end of a circuit P type side to the positive end, and the free electrons and the N type material are repelled by the negative side because again you know like charge repels like yes, they're drawn to the positive end, and you then complete the circuit and you get this um you get this electron movement.

If you try to go the other way, it wouldn't work because the negatively charged particles going into the positive end would just fill up the holes and then it would stop. So a diode is kind of like a one way street and electronics. If you hook up a diode, uh current can only flow in one direction and it will not flow the other way. So if you even if you reversed the current, it would not complete the circuit if it went against the diode, Reversing the polarity

just won't work, captain. So so that's your basic led. But visible light emitting diode are made up of materials that create a a wide gap between where the hole is and where the electrons are, so that when the electrons move through they do emit, They give off photons because again we're talking about when electrons are moving down through the orbitals. Uh, you know, you you've given them enough energy for them to to move out of their

normal orbitals. Once they move down, they give off light. Well, the greater that gap is, the more light they give off. So if you create a visible light emitting diode and you use these materials that create these wider gaps between the conduction band and the lower orbitals of the electrons, that gap is what allows the electrons to give off light.

And in general, these l e d s tend to look if you look at a single LED, they tend to look like a miniature light bulb light Christmas saying, now there's no filament in there, because again you're just what all you're doing is you're allowing those electrons to move in those those um orbitals and that's what's giving off the photons. And these little light bulbs tend to be shaped in such a way that it guides the light that's emitted in a very particular direction, so that

way it's a very concentrated light. So if you see an LED light fixture, and this could be you know, an LED light bulb or on on the back of cars. I've seen a lot of um uh tail lights in recent cars that use L E D s And you

can tell because it will be a group of them together. Um. And so it looks like there are lots of little tiny dots of light in a pattern you know, maybe a um a series of concentric circle type things, or or you know some other kind of thing um, and it's you can you can tell that it's an LED light specifically because you can see the little dots. But together, when they work together like that, they can be very bright. I have a couple of LED flashlights as a matter

of fact, um that you know. You it's like, hey, does this thing work? Oh you know? Um. However, they're very efficient. Yes, yes, I've got a couple of LED lights in my house. Actually, there are a couple of light fixtures that were specifically designed to work with L A D lights and um, yes, they are incredibly efficient,

particularly compared to incandescence and even fluorescence. But we didn't really mention, but florescent lights are more efficient than incandescent light bulbs, They last longer, they use less energy to create light. They don't they don't lose as much energy in producing heat. So yeah, so they don't heat up as hot as an incandescent bulb. That's not saying that a fluorescent bulb is going to be cool to the touch, it's just not going to be as hot as an

incandescent bulb. Is l e ED is even more efficient. Uh, it has a much higher luminous efficacy, if you will. As we say in our article on l E D sage. I'm sorry, um, but they talked about how in our article they mentioned a specific type of LED light bulb. In this case, it was the Sewel's Evo lux LED bulb, which produces seventy six point nine lumens per what, which is essentially how bright This is dependent upon how much

energy you're putting into it. Whereas an incandescent bulb is seventeen lumens per what, So seventy six point nine for seventeen. It shows that the efficiency of the l e ED is far greater than that of the incandescent bulb. And the LED lifetime can be around fifty thousand hours, So compare that to a couple of thousand hours for a typical incandescent bulb, and that's a big difference. Now, LED light bulbs do tend to be much more expensive than

incandescent or fluorescent bulbs. However, if you measure that across the lifetime of the bulb and you factor in things like energy savings, uh, they on the long term can be a good investment. However, the upfront cost is still much higher, so that can be a barrier for a lot of people. The cost has been decreasing uh quite a bit since over the last decade or so, since

semiconductor material has become much more cost effective. Is when these first came out, semiconductor material was a precious commodity. It was not something that was mass produced. It was not something that you could easily get your hands on, and so it was much more expensive. But just as Gordon More predicted way back in the sixties, the manufacturing processes would mean that costs would come down, efficiencies go up, and as a result, we're able to get more efficient products.

Now he was talking specifically about integrated circuits, but as it turns out, that kind of applies to lots of stuff. Doesn't necessarily mean that the light bulbs will have next year will be twice as bright as the ones we have this year. So the analogy doesn't continue all the way there, but it's still I think semi applicable. Uh.

So yeah, you can see the differences between these these approaches. Uh. Ultimately, it's all about again exciting atoms, and once those aboms get excited, they just light up, just like Chris does whenever I talk about Inner Space, his favorite movie. His face is lighting up right now. People, if you could call it that, Yeah, it's uh, it's funny. They're they're so excited and they just can't hide it. That's true.

They're about to lose control. They think they like it, they think alright, So that wraps up I think this discussion. Unless you have anything else you want to add to light bulbs, Nope, all right, let's sign off. You guys can switch off the lights now. We're gonna wrap this up. You guys. If you have any topics you would like us to tackle in future episodes of tech Stuff, shoot us an email that addresses tech Stuff at Discovery dot com,

or let us know on Facebook or Twitter. You can find us there with the handle text stuff hs W and Chris and I will thought you again really soon. For more on this and thousands of other topics. Is it how stuff works. Dot com